Abstract
Enteroaggregative Escherichia coli (EAEC) is a significant cause of acute and chronic diarrhea, foodborne outbreaks, infections of the immunocompromised, and growth stunting in children in developing nations. There is no vaccine and resistance to antibiotics is rising. Unlike related E. coli pathotypes that are often associated with acute bouts of infection, EAEC is associated with persistent diarrhea and subclinical long-term colonization. Several secreted virulence factors have been associated with EAEC pathogenesis and linked to disease in humans, less certain are the molecular drivers of adherence to the intestinal mucosa. We previously established human intestinal enteroids (HIEs) as a model system to study host-EAEC interactions and aggregative adherence fimbriae A (AafA) as a major driver of EAEC adherence to HIEs. Here, we report a large-scale assessment of the host response to EAEC adherence from all four segments of the intestine across at least three donor lines for five E. coli pathotypes. The data demonstrate that the host response in the duodenum is driven largely by the infecting pathotype, whereas the response in the colon diverges in a patient-specific manner. Major pathways altered in gene expression in each of the four enteroid segments differed dramatically, with responses observed for inflammation, apoptosis and an overwhelming response to different mucin genes. In particular, EAEC both associated with large mucus droplets and specific mucins at the epithelial surface, binding that was ameliorated when mucins were removed, a process dependent on AafA. Pan-screening for glycans for binding to purified AafA identified the human ligand as heparan sulfate proteoglycans (HSPGs). Removal of HSPG abrogated EAEC association with HIEs. These results may mean that the human intestine responds remarkably different to distinct pathobionts that is dependent on the both the individual and intestinal segment in question, and uncover a major role for surface heparan sulfate proteoglycans as tropism-driving factor in adherence and/or colonization.
Highlights
Enteroaggregative E. coli (EAEC) is a heterogeneous group of enteric bacteria that is a major cause of acute and persistent diarrhea, illness and death among children in developing countries that was originally isolated from children in Peru [1]
We observed a major upregulation of host mucins, for EAEC, which led to the identification of heparan sulfate proteoglycans (HSPGs) as the receptor on human colonoids
Some of the pathogenesis of EAEC may be related to a number of secreted protein effectors or toxins that are commonly associated with this diarrheal pathotype, including the serine protease autotransporters of Enterobacteriaceae (SPATES), [10,11,12]: ShET1 [13], Pic [14, 15], Pet [16], heat-stable enterotoxin 1 (EAST1) [17], hemolysin E (Hly1) [18], and dispersin [19]
Summary
Enteroaggregative E. coli (EAEC) is a heterogeneous group of enteric bacteria that is a major cause of acute and persistent diarrhea, illness and death among children in developing countries that was originally isolated from children in Peru [1]. The clinical symptoms of EAEC infection include watery diarrhea [5] or bloody diarrhea [6], sometimes fever and mucoid stools [5]. Some of the pathogenesis of EAEC may be related to a number of secreted protein effectors or toxins that are commonly associated with this diarrheal pathotype, including the serine protease autotransporters of Enterobacteriaceae (SPATES), [10,11,12]: ShET1 [13], Pic [14, 15], Pet [16], heat-stable enterotoxin 1 (EAST1) [17], hemolysin E (Hly1) [18], and dispersin [19]. There is no vaccine for EAEC or related diarrheal E. coli in general, studies have focused on secreted toxins from related pathotypes [4, 20, 21]. Of great concern is the acquisition of virulence factors such as Shiga toxin, an event that contributed to the widespread outbreak in Europe in 2011 that sickened greater than three-thousand people and killed about fifty [25,26,27]
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